1) Field of the Invention
The present invention relates to swallowable and capsule-shaped endoscopes and a capsule endoscope system.
2) Description of the Related Art
Swallowable and capsule-shaped endoscopes are known in the art. A patient swallows such a capsule endoscope and as the capsule endoscope passes through an abdominal cavity, it captures images of a stomach, intestines etc. An example of such a capsule endoscope is described below with reference to FIG. 9.
As shown in FIG. 9, the conventional capsule endoscope includes a watertight capsule casing 8 having a front cover 5. The capsule casing 8 houses an image capturing unit 1 that captures images of an inside the abdominal cavity, an illuminating unit 2 that outputs a light to illuminate the inside of the abdominal cavity, a power-supply unit 3 that supplies power to the image capturing unit 1 and the illuminating unit 2.
The illuminating unit 2 and the image capturing unit 1 are disposed near each other and they face toward a front side through the front cover 5. The front cover 5 is partly or fully transparent so that when the illuminating unit 2 outputs the light, the light illuminates the inside of the abdominal cavity and the image capturing unit 1 can capture images of inside of the abdominal cavity.
The front cover 5 is semispherical, because, it is easier for a patient to swallow the capsule endoscope if the front cover 5 is semispherical, and body fluids can not remain on the front cover 5 if the front cover 5 is semispherical (see Japanese Patent Application Laid-open Publication No. 2001-95756).
However, the illuminating unit 2 disclosed in Japanese Patent Application Laid-open Publication No. 2001-95756 has problems as explained below. As shown in FIG. 10, when many illuminating units 2 are arranged around the image capturing unit 1 on a circle, light from all the illuminating units 2 overlap at a portion that is in front of the image capturing unit 1 and the portion where the lights overlap is brighter that the portion where there is no overlap.
Because of the unbalance in the brightness, the image quality of the images captured by the image capturing unit degrades and good diagnosis becomes difficult.